Evolution / Genetics / Biology

New revelations in tracing indigenous DNA

The sequencing of the DNA of an ancient species of human has provided more clues to the evolutionary history of modern humans.

The indigenous peoples of Oceania have some percentage of Denisovan ancestry [Credit: Mike Keesey]

A team of scientists in Germany recently published the results of their new method of genetic analysis, in which they reconstructed the entire genome of little-known hominins, the Denisovans.

Using material gleaned from a tiny finger bone and two teeth found in a cave in eastern Siberia, the scientists found Denisovans shared a common ancestor with both Neanderthals and modern humans.

But it was the revelation that Australia's Indigenous people, along with Melanesians living in Papua New Guinea and nearby islands, have a more recent connection with Denisovans that has raised eyebrows.

Scientists at the Max Planck Institute for Evolutionary Anthropology in Liepzig, Germany developed a revolutionary new technology that allowed them to analyse the tiniest DNA strands from the Denisovan finger bone.

Earlier analysis had already ascertained it was from an ancient species that was neither modern human nor Neanderthal.

They've found it belonged to a young, brown-eyed girl whose body has lain in the cave in Denisova, Russia for around 80-thousand years.

Little else can be definitively known about her, but her DNA shows Denisovans were closely related to, but distinct from, Neanderthals.

And it also shows that while all modern humans except Africans have Neanderthal genes, only people with Melanesian ancestry have Denisovan DNA.

A researcher at the Institute, Mark Stoneking, speaking to the ABC, explains.

"The amount of Denisovan ancestry in native Australians and New Guineans we estimate at somewhere around four to six percent. And if that is indeed the case, then that is also I think a bit extraordinary, because that means that Denisovans were more widespread than any other hominin with the exception of us."

It's changed the way scientists think about human migration across the world.

The scientist leading the research is paleogeneticist Svante Paabo.

Speaking at an online conference, Dr Paabo says we're now beginning to get a picture of what the world looked like when modern humans started coming out of Africa.

"In the West there were Neanderthals, in the East there were Denisovans, maybe other forms of humans too that we've not yet described. The modern humans emerged somewhere in Africa, came out of Africa presumably in the Middle East. They meet Neanderthals, mix with them, continue to spread over the world. And somewhere in south-east Asia they meet Denisovans, mix with them, and continue on out through the Pacific."

But not everyone is convinced the DNA results prove interbreeding between species of human.

Darren Curnoe, an evolutionary biologist and anthropologist at the University of New South Wales says the genome sequencing could be telling a story about interbreeding or it could just show how human genes have mutated over millennia.

"It is controversial. I think there are many of us who are taking a sceptical line, not because we have any particular opposition to the idea that our ancestors may have bred with other species. It's more that it's such a new area and the technology is moving at a very rapid pace. and the comparisons that have been done with living human genomes, if you like, are quite limited at the moment. So many of us are looking for many more comparisons, more accuracy in the data. And we want to see particularly comparisons done with members of our species who are also tens of thousands, maybe a hundred thousand years old as well."

What do Indigenous people think about revelations their DNA has that unique Denisovan link?

Mitchella Hutchens, is a Wardandi Yorga woman from the south-west of Western Australia.

Her family has been working closely with archaeologists and genetic scientists excavating caves in that region.

The work currently focuses on plant and animal remains, but the scientific team has broached the possibility of finding ancient human remains and testing to assess links to Indigenous people living in the area today.

Mitchella Hutchens says the more scientists find about early human populations in Australia, the more Indigenous oral history is vindicated.

"We like to challenge the scientists and we enjoy them actually coming up with new theories. We've been told that basically, in the beginning we were only 18,000 years old. They re-discovered something else and said we were 24.000 years old, and as the discoveries went on, it's gone way past that in the latest case studies. So we explain to them that from our traditional point of view we've always come from this country and our spirit was born from the land that the ancients came from."

Michael Westaway is the head of cultural environments at the Queensland Museum.

He's involved in a project comparing DNA of ancient humans found in southern Asia and Australian Indigenous people, particularly in the Lake Mungo area of western New South Wales.

Dr Westaway says there was concern behalf of Indigenous people when scientists first started talking about mapping the human genome.

But his team has had the opposite experience, after taking time to talk to Aboriginal people about the significance of the studies and what information they can reveal.

"Some groups aren't very positive, but others are quite supportive and very keen to find out more. The whole question that perhaps ancient populations moving through central Asia sometime after 100,000 years ago interacted with our cousins which are now extinct. I mean I think that's a fascinating thing and a lot of people are interested in their origins. There are a lot of different ways we can look at origins. We can look at them through science, we can look at them through Christian beliefs or Islamic beliefs and we can also look at them through Aboriginal origin stories and the Dreaming. So these things don't necessarily have to be in conflict. I think they're actually quite complementary in many regards."

Cultural anthropologist Emma Kowal of the University of Melbourne, says population genetics is not a field of research many Australian Aboriginal people consider especially relevant to their lives.

But Dr Kowal says Indigenous people she's worked with do not feel threatened by the latest discoveries in DNA research.

"It certainly hasn't been the kind of strong negative reaction that we have seen, for instance, in the United States where a number of aboriginal groups have stopped DNA research on human remains and DNA research completely because of concerns that the scientific story of human migration is in conflict with their cosmological beliefs that people came from that place."

For Indigenous woman Mitchella Hutchens, there's nothing remotely disconcerting about being linked by genes to people present and past from other parts of the world.

"From all our ancient teachings in my particular family we've always been taught that we are universal people sharing one nest. It doesn't matter what colour you are. We've just got to look after the nest and look after each other. For us, the amusing part of it is we tell people facts and quite often they have to have the scientific proof to be able to put our facts forward. So every time they do prove one of our facts true it sort of reinforces our stories and what we've been saying to them. So I guess there's a flip-side to it, too."